Using "With" and BelongsTo on a model which has a defined table name causes a NULL to be returned - eloquent

Question

What I am finding is that the "picker" data does not get returned when using "with" but does if I use the default lazy loading query. It seems it might be down to the fact that the "picker" table uses a table name of "users".
So I have the following tables.
USERS [id, name]
PRODUCTS [id, name, picker_id]
I have created the following models.
class User extends BaseModel {
protected $hidden = array('pivot');
public function roles() : \Illuminate\Database\Eloquent\Relations\BelongsToMany {
return $this->belongsToMany(Role::class);
}
}
class Product extends BaseModel {
public function picker() : \Illuminate\Database\Eloquent\Relations\BelongsTo {
return $this->belongsTo(Picker::class);
}
}
class Picker extends User {
protected $table = 'users';
public function products() : \Illuminate\Database\Eloquent\Relations\HasMany {
return $this->hasMany(Product::class, 'picker_id');
}
public function pickingSequence() : \Illuminate\Database\Eloquent\Relations\HasOne {
return $this->hasOne(PickingSequence::class);
}
protected static function boot() {
parent::boot();
static::addGlobalScope('status', function (\Illuminate\Database\Eloquent\Builder $builder) {
$builder->join('role_user', 'role_user.user_id', '=', 'users.id')
->where('role_user.role_id', '=', Role::PICKER);
});
}
}
The picker and user models are using the same table (users), however the picker model filters out users so only those that have the correct role of "picker" are found. Working great so far.
What I want to do is to get all products and their relevant pickers (a product has one picker, a picker has multiple products).
Product::with('picker')->get()
This returns NULL for "picker", yet if I do:
Product::first()->picker
This works so the relationship seems fine and returns:
array(6) { ["id"]=> int(5) ["name"]=> string(8) "Picker B"
["created_at"]=> NULL ["updated_at"]=> NULL ["user_id"]=>
int(3) ["role_id"]=> int(1) }
If I change the "product" model to add a debug message It shows the relationship is working:
class Product extends BaseModel {
public function picker() : \Illuminate\Database\Eloquent\Relations\BelongsTo {
debug($this->belongsTo(Picker::class)->first());
return $this->belongsTo(Picker::class);
}
}
I am using the same syntax using "with" on other queries without a problem just can't seem to see the issue.
By changing the "belongsTo" inside the "Product" class to the following:
return $this->belongsTo(User::class, 'picker_id');
This now works and returns the picker data but I am using the wrong model, the "picker" model extends the user model.